Enclosure for a multi-channel modulator driver

ABSTRACT

Embodiments of the present disclosure describe techniques and configurations for an enclosure that can be used for channel isolation in a multi-channel modulator driver such as, for example, an optical modulator driver. A system may include a substrate, a multi-channel modulator driver mounted on the substrate, and an enclosure mounted on the substrate to cover the multi-channel modulator driver, the enclosure having a wall that is disposed between first components of the multi-channel modulator driver associated with a first channel and second components of the multi-channel modulator driver associated with a second channel, the wall being composed of an electrically conductive material. Other embodiments may also be described and/or claimed.

This application is a Divisional of U.S. patent application Ser. No.13/309,424, filed Dec. 1, 2011, the disclosure of which is incorporatedherein by reference in its entirety.

FIELD

Embodiments of the present disclosure generally relate to the field ofradio-frequency (RF) emitting integrated circuits, and moreparticularly, to an enclosure for a multi-channel driver such as amultichannel modulator driver.

BACKGROUND

The development of transponder technology is rapidly accelerating tomeet high data rate needs of next-generation optical carrier networks.Emerging transponders may, for example, use multi-level DualPolarization Quadrature Phase Shift Keying (DP-QPSK) modulation schemesto improve optical spectral efficiency. The emerging transponders mayinclude multiple radio frequency data input ports that utilizemulti-channel modulator drivers. The multi-channel modulator drivers maybe positioned such that radio-frequency (RF) emitting componentsassociated with different channels interfere with one another (e.g.,cross-channel coupling). Techniques and configurations to isolate thechannels and reduce such interference may be desirable.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be readily understood by the following detaileddescription in conjunction with the accompanying drawings. To facilitatethis description, like reference numerals designate like structuralelements. Embodiments are illustrated by way of example and not by wayof limitation in the figures of the accompanying drawings.

FIG. 1 schematically illustrates a top view of a system including anenclosure for a multi-channel modulator driver, according to variousembodiments.

FIG. 2 is a graph of Isolation versus Resistivity for various materials,according to various embodiments.

FIG. 3 schematically illustrates a top perspective view of an enclosure,according to various embodiments.

FIG. 4 schematically illustrates a top view of another system includingmultiple enclosures for multiple multi-channel modulator drivers,according to various embodiments.

FIG. 5 schematically illustrates a top view of yet another systemincluding a single enclosure having multiple walls for a multi-channelmodulator driver, according to various embodiments.

FIG. 6 schematically illustrates a bottom perspective view of anenclosure, according to various embodiments.

FIG. 7 schematically illustrates a bottom perspective view of theenclosure of FIG. 6 having a metal film disposed on a wall of theenclosure, according to various embodiments.

FIG. 8 schematically illustrates a bottom perspective view of anenclosure having an alternative wall configuration, according to variousembodiments.

FIG. 9 is a flow diagram of a method for fabricating a system describedherein, according to various embodiments.

DETAILED DESCRIPTION

Embodiments of the present disclosure describe techniques andconfigurations for an enclosure that can be used for a multi-channelmodulator driver such as, for example, an optical modulator driver. Inthe following detailed description, reference is made to theaccompanying drawings which form a part hereof, wherein like numeralsdesignate like parts throughout, and in which is shown by way ofillustration embodiments in which the subject matter of the presentdisclosure may be practiced. It is to be understood that otherembodiments may be utilized and structural or logical changes may bemade without departing from the scope of the present disclosure.Therefore, the following detailed description is not to be taken in alimiting sense, and the scope of embodiments is defined by the appendedclaims and their equivalents.

For the purposes of the present disclosure, the phrase “A and/or B”means (A), (B), or (A and B). For the purposes of the presentdisclosure, the phrase “A, B, and/or C” means (A), (B), (C), (A and B),(A and C), (B and C), or (A, B and C).

The description may use the phrases “in an embodiment,” or “inembodiments,” which may each refer to one or more of the same ordifferent embodiments. Furthermore, the terms “comprising,” “including,”“having,” and the like, as used with respect to embodiments of thepresent disclosure, are synonymous. The term “coupled” may refer to adirect connection, an indirect connection, or an indirect communication.

Various operations are described as multiple discrete operations inturn, in a manner that is most helpful in understanding the claimedsubject matter. However, the order of description should not beconstrued as to imply that these operations are necessarily orderdependent. In particular, these operations may not be performed in theorder of presentation. Operations described may be performed in adifferent order than the described embodiment. Various additionaloperations may be performed and/or described operations may be omittedin additional embodiments.

The description may use perspective-based descriptions such asover/under, or top/bottom. Such descriptions are merely used tofacilitate the discussion and are not intended to restrict theapplication of embodiments described herein to any particularorientation.

FIG. 1 schematically illustrates a top view of a system 100 including anenclosure 102 for a multi-channel modulator driver, according to variousembodiments. The enclosure 102 is configured to cover components 104 ofa first channel of the multi-channel modulator driver and components 106of a second channel of the multi-channel modulator driver that arecoupled to a substrate 108, which may be referred to as a packagesubstrate. The components 104, 106 are depicted in dashed form toindicate that they underlie a top region (e.g., Top Region of FIG. 3) ofthe enclosure 102, which is not shown in FIG. 1 for the sake of clarity.The first channel may be an “I” channel and the second channel may be a“Q” channel as commonly used in the field of optical drivers, in someembodiments.

The components 104, 106 may include components that, when in operation,emit radio frequency (RF) energy. For example, the components 104, 106may include one or more amplifiers such as, for example, one or moredistributed amplifiers 112. In some embodiments, the components 104, 106each include three distributed amplifiers (e.g., broadband distributedamplifiers), as depicted. The three distributed amplifiers of each ofthe corresponding components 104, 106 may each correspond with a stageof an amplifying cascade and may include one or more microwaveintegrated circuits (MICs) in some embodiments. In some embodiments,each stage of the amplifying cascade may have an inductor. In someembodiments, the components 104, 106 may include components for one ortwo stages or greater than three stages.

The components 104, 106 may further include one or more capacitors suchas, for example, one or more bypass capacitors 114 and/or one or moreDirect Current (DC) blocking capacitors 116. In some embodiments, thecomponents 104, 106 include two bypass capacitors and two DC blockingcapacitors per amplifier.

The components 104, 106 may further include one or more inductors 118.In one embodiment, the components 104, 106 each include one inductor.The one or more inductors 118 may be packaged external to the enclosure102 in some embodiments. The components 104, 106 may include additionalfeatures such as, for example, routing features (not shown) such astraces or wirebond structures that facilitate electrical connectionsbetween the components 104, 106, the substrate 108, and other devices(e.g., printed circuit board 120, modulator 122). More or lesscomponents 104, 106 than depicted can be used in other embodiments.

The enclosure 102 may be coupled to the substrate 108 using an adhesive.In some embodiments, a peripheral region (e.g., Peripheral Region ofFIG. 3) of the enclosure 102 is attached to the substrate 108 using anelectrically insulative adhesive such as an epoxy. According to variousembodiments, a combination of electrically conductive and non-conductiveadhesive may be used to obtain a desired level of performance andcross-channel isolation.

In an embodiment, the enclosure 102 includes at least one wall(hereinafter “wall 110”) configured to isolate the components 104 of thefirst channel from the components 106 of the second channel. The wall110 may extend from the top region of the enclosure 102 to the substrate108 and may be disposed between components 104 of the first channel andcomponents 106 of the second channel. The wall 110 may be attached tothe substrate 108 using an adhesive. The first and second channels maybe separated by a distance of approximately 2.5 millimeters (mm) in someembodiments. The first and second channels may be separated by greateror shorter distances in other embodiments.

In various embodiments, the enclosure 102 and the wall 110 are composedof an electrically conductive polymer. The electrically conductivepolymer may be selected for fabrication of the enclosure 102 based on asurface resistivity (e.g., per test method of the InternationalElectrotechnical Commission (IEC) 93) of the polymer that providesadequate isolation between adjacent channels of a multi-channelmodulator driver. For example, referring briefly to FIG. 2, a graph 200depicts Isolation (dB) versus Surface Resistivity (Ohms) for variousmaterials, according to various embodiments. As can be seen, a range(e.g., Range Acceptable Resistivity) from about 10 Ohms to about 5000Ohms of surface resistivity may be capable of providing about −30decibel (dB) of broadband isolation between adjacent channels of amulti-channel modulator driver. According to various embodiments, theenclosure 102 and wall 110 described herein may provide −30 dBcross-channel isolation across a wide frequency band extending from 0Hertz (Hz) or DC to at least 50 GHz.

Returning again to FIG. 1, the electrically conductive polymer of theenclosure 102 and wall 110 may be formed by blending a variety ofconductive materials into a base polymer material. For example,electrically conductive fillers such as carbon fiber, carbon black,steel fiber, nickel fiber, other metal fiber or particles, orcombinations thereof, may be added to a polymer to increase electricalconductivity. Other suitable electrically conductive fillers can be usedin other embodiments. In some embodiments, the electrically conductivepolymer may have a surface resistivity ranging from 10 Ohms to 5000 Ohmsor in some embodiments 200 Ohms to 1200 Ohms.

In some embodiments, the enclosure 102 may resist softening at atemperature of at least 260° C., which may be a temperature conditionassociated with a solder reflow process that may be used to attach thesubstrate 108 or other components to the printed circuit board 120. Theenclosure 102 may resist softening at temperatures up to approximately260° C. In some embodiments, the enclosure 102 may be composed of aconductive filler (e.g., 30% by weight) such as carbon fiber or carbonblack and at least one of liquid crystal polymer (LCP) or polyetherether ketone (PEEK). The electrically conductive polymer may be suitablefor use with an injection molding process that may be used to fabricatethe enclosure 102. An enclosure 102 composed of an electricallyconductive polymer may eliminate or reduce a need for application of anadditional absorber material to provide channel isolation.

In some embodiments, the wall 110 may further include a film 124composed of an electrically conductive material such as, for example,metal disposed on at least a portion of the wall 110 up to and includingan entire surface of the wall 110 (e.g., from a surface of the wall 110that adjoins the top region of the enclosure 102 to a surface of thewall 110 that is coupled to the substrate 108). The film 124 may furtherincrease isolation between the first channel and second channel relativeto a similarly configured all metal wall, which may exhibit degradedchannel isolation relative to a wall having only the electricallyconductive polymer or a wall having an electrically conductive polymercovered by the film 124. According to various embodiments, the film 124includes a metal such as, for example, aluminum, silver, gold, nickel,or copper having a thickness ranging from a single atomic layer to 40mils (1 mil=a thousandth of an inch). The film 124 may be composed ofother metals or other suitable electrically conductive materials and/ormay have other thicknesses in other embodiments.

In some embodiments, the wall 110 is only partially covered with thefilm 124. For example, the film 124 may be disposed to only cover theportion of the wall 110 that is directly between components (e.g., oneor more distributed amplifiers 112) of the first channel and the secondchannel that emit RF energy. In the depicted embodiment, a region of thewall 110 (e.g., between the one or more inductors 118 of the first andsecond channels) that is not directly between the distributed amplifiers112 is not covered by the film 124. Thus, in some embodiments, the film124 does not cover at least a portion of the wall 110. Partiallycovering the wall 110 with the film 124 may further increase channelisolation relative to a wall 110 that is completely covered with thefilm 124. In some embodiments, the portion of the wall 110 that iscovered with the film 124 has a length (e.g., left to right in FIG. 1)of about 11 mm and the portion of the wall 110 that is not covered withthe film 124 has a length of about 5 mm. In other embodiments, the oneor more inductors 118 may be packaged external to the enclosure 102. Insuch embodiments, the wall 110 may be covered entirely with the film124.

According to various embodiments, the substrate 108 is generallycomposed of an epoxy-based material and may include glass and/or ceramicfiller or any other suitable material for high frequency RFapplications. In one embodiment, the substrate 108 includes a groundstructure such as, for example, ground strip 126. The ground strip 126is composed of an electrically conductive material such as, for example,a metal that is electrically coupled to a ground voltage supply (notshown) such as, for example, RF ground. In the depicted embodiment, theground strip 126 traverses a length of the substrate 108, between thecomponents 104, 106, that corresponds with a length of the wall 110.

The wall 110 including the film 124, if used, may be electricallycoupled to the ground strip 126. For example, the wall 110 may beelectrically coupled to the ground strip 126 using an electricallyconductive adhesive such as, for example, silver epoxy or paste to bondthe film 124 and/or wall 110 with the ground strip 126. Electricallycoupling the wall 110 to the ground strip may increase channel isolationrelative to an enclosure 102 that is not electrically coupled to ground.The ground strip 126 may have other shapes or configurations in otherembodiments. For example, the ground strip 126 may be configured toprovide electrical contact for only a portion of the wall 110.

The substrate 108 may further include routing features (not shown) toroute electrical signals between the multi-channel modulator driver andthe printed circuit board 120. Although in the top view of FIG. 1 andtop perspective view of FIG. 3, the substrate 108 extends to a positionexternal and beyond the peripheral region (e.g., Peripheral Region ofFIG. 3) of the enclosure 102, in other embodiments, the substrate 108has a size that is coextensive with the peripheral region such that thesubstrate 108 does not extend beyond the peripheral region of theenclosure 102.

According to various embodiments, the substrate 108 is mounted on theprinted circuit board 120. The substrate 108 may be mounted, forexample, using conventional surface mount technology. The printedcircuit board 120 may include input connectors 132, 134 that routesignals to respective components 104, 106 of the first and secondchannels and output connectors 128, 130 that route signals from therespective components 104, 106 to modulator 122. The modulator 122 maybe, for example, an optical modulator capable of operating at 100Gigabytes (Gb)/second. The system 100 may include other types ofmodulators 122 in other embodiments.

FIG. 3 schematically illustrates a top perspective view of an enclosure102, according to various embodiments. The enclosure 102 may be mountedon a substrate 108. In some embodiments, the enclosure 102 includes atop region (e.g., Top Region) and peripheral region (e.g., PeripheralRegion), as can be seen. The peripheral region may include surfaces thatare coupled to the substrate using, e.g., an adhesive. The top regioncovers components disposed within the enclosure 102. The enclosure 102may include other shapes (e.g., non-rectangular) in other embodiments.

FIG. 4 schematically illustrates a top view of another system 400including multiple enclosures 102, 202 for multiple multi-channelmodulator drivers, according to various embodiments. According tovarious embodiments, the system 400 includes an enclosure 102 that maybe a first enclosure coupled to a substrate 108 and having a wall 110that provides channel isolation between components 104 of a firstchannel of a multi-channel modulator driver and components 106 of asecond channel of the multi-channel modulator. The system 400 mayfurther include an enclosure 202 that may be a second enclosure coupledto another substrate 208 and having another wall 210 that provideschannel isolation between components 204 of a first channel of anothermulti-channel modulator driver and components 206 of a second channel ofthe other multi-channel modulator driver.

Enclosure 202, components 204, 206, substrate 208, wall 210, film 224,and ground strip 226 may comport with embodiments described inconnection with respective enclosure 102, components 104, 106, substrate108, wall 110, metal film 124, and ground strip 126 of FIG. 1.Substrates 108 and 208 may be separate components mounted on the printedcircuit board 120.

The printed circuit board 120 may include additional input connectors232, 234 that route signals to the respective components 204, 206 of thefirst and second channels of the other multi-channel modulator driverand additional output connectors 228, 230 that route signals fromrespective components 204, 206 to modulator 122. According to variousembodiments, the system 400 represents a quad channel system consistingof two dual channel drivers. The system 400 may be expanded to includeadditional channel modulator drivers in other embodiments.

FIG. 5 schematically illustrates a top view of yet another system 500including a single enclosure 302 having multiple walls 310, 410, 510 fora multi-channel modulator driver, according to various embodiments. Insome embodiments, components 304, 306, 404, 406 of a respective firstchannel, second channel, third channel, and fourth channel of amulti-channel modulator driver are mounted on a single substrate 308.The enclosure 302 may include a wall 310 to provide channel isolationbetween components 304 and 306 and wall 410 to provide channel isolationbetween components 404 and 406. The enclosure 302 may further includewall 510 to provide channel isolation between components 306 and 404.

Enclosure 302, components 304, 306, 404, 406, substrate 308, walls 310,410, 510, metal film 324, 424, 524 and ground strips 326, 426, 526 mayeach comport with embodiments described in connection with respectiveenclosure 102, components 104, 106, substrate 108, wall 110, metal film124, and ground strip 126 of FIG. 1. Substrate 308 may be a singlecomponent mounted on the printed circuit board 120.

The printed circuit board 120 may include input connectors 332, 334 thatroute signals to the respective components 304, 306 of the first andsecond channels of the multi-channel modulator driver and outputconnectors 328, 330 that route signals from the respective components304, 306 to modulator 122. The printed circuit board 120 may furtherinclude input connectors 432, 434 that route signals to respectivecomponents 404, 406 of the third and fourth channels of themulti-channel modulator driver and output connectors 428, 430 that routesignals from the respective components 404, 406 to modulator 122.

According to various embodiments, the system 500 may represent anotherconfiguration for a quad channel system consisting of two dual channeldrivers. In some embodiments, the system 500 may include three or morechannels of a multi-channel modulator driver. A wall (e.g., wall 310,410, or 510) may be disposed between components (e.g., components 304,306, 404, 406) of each channel of the multi-channel modulator. Thesystem 500 may be expanded to include additional channel modulatordrivers in other embodiments.

FIG. 6 schematically illustrates a bottom perspective view of anenclosure 102, according to various embodiments. For example, the bottomperspective view may be an opposite view of the enclosure 102 depictedin FIG. 3.

In some embodiments, the enclosure 102 may be configured for attachmentto a substrate (e.g., substrate 108 of FIG. 1) to cover a multi-channelmodulator driver mounted on the substrate. According to variousembodiments, the enclosure 102 may include a top region, a plurality ofperipheral regions coupled with the top region, and a wall 110. The wall110 may be coupled with the top region and first and second peripheralregions of the plurality of peripheral regions, as can be seen, to forma first cavity 650 and a second cavity 675. The enclosure 102 may beconfigured to be coupled with a substrate with components (e.g.,components 104 of FIG. 1) of a first channel of a multi-channelmodulator driver disposed in the first cavity 650 and components (e.g.,components 106 of FIG. 1) of a second channel of the multi-channelmodulator driver disposed in the second cavity 675

The enclosure 102 may include one or more fin structures 640. In someembodiments, the one or more fin structures 640 may extend from aperipheral region (e.g., a third and/or fourth peripheral region) of theenclosure towards the wall 110, as can be seen. In some embodiments,each of the one or more fin structures 640 is configured to extendbetween RF-emitting components of a channel when the enclosure 102 iscoupled to a substrate. For example, in some embodiments, a fin of theone or more fin structures 640 is configured to extend between eachamplifier of a plurality of amplifiers of a channel (e.g., one or moredistributed amplifiers 112 of FIG. 1) when the enclosure 102 is coupledto a substrate. In some embodiments, each of the one or more finstructures 640 extends between at least two amplifiers of the channel.The one or more fin structures 640 may extend from the top region and/orfrom the wall 110 in other embodiments.

According to some embodiments, the enclosure 102 including the wall 110and one or more fin structures 640 are part of a single, continuousmaterial structure. For example, the enclosure 102, the wall 110, andthe one or more fin structures 640 may be simultaneously formed using aninjection molding process. The one or more fin structures 640 maycomprise an electrically conductive polymer that is used to fabricatethe enclosure 102 in some embodiments.

FIG. 7 schematically illustrates a bottom perspective view of theenclosure 102 of FIG. 6 having a film 124 of metal disposed on a wall110 of the enclosure 102, according to various embodiments. As can beseen, the film 124 may be disposed on at least a portion of the wall110. The film 124 may extend to cover a surface of the wall 110 thatadjoins the top region of the enclosure 102, as can be seen, and maywrap around a surface, S1, of the wall 110 that may be coupled to thesubstrate using an electrically conductive adhesive. At least a portionof the surface S1 may be covered with the film 124 in some embodiments.In some embodiments, the electrically conductive adhesive may be appliedto cover the entire surface S1 including portions of the surface S1covered with the film 124 and portions of the surface S1 that are notcovered with the film 124 to provide electrical contact between thesurface S1 of the wall 110 and the ground strip (e.g., ground strip 126)along the entire surface S1. A surface, S2, of the peripheral region maybe coupled to the substrate using an electrically insulative adhesive.

FIG. 8 schematically illustrates a bottom perspective view of anenclosure 102 having an alternative wall configuration, according tovarious embodiments. In FIG. 8, the wall 110 is configured to have afirst portion 110 a that extends to structurally support, secure, orfasten a second portion 110 b that may be fabricated as a separatecomponent and attached between the first portion 110 a and a peripheralregion of the enclosure 102 to complete the wall 110. In someembodiments, the second portion 110 b is covered with a film 124 ofmetal and the first portion 110 a does not have any film of metal on thesurface at all. Such configuration may facilitate depositing orotherwise attaching the film 124 to the second portion 110 b prior toattaching the second portion to the enclosure 102 when the secondportion 110 b is separate from the enclosure 102. The second portion 110b may be coupled to the enclosure 102 including, for example, the firstportion 110 a using any suitable technique. In some embodiments, thesecond portion 110 b may be entirely composed of an electricallyconductive material such as a metal including, for example, copper orbrass. Other electrically conductive materials can be used in otherembodiments.

FIG. 9 is a flow diagram of a method 900 for fabricating a system (e.g.,system 100 of FIG. 1) described herein, according to variousembodiments. At 902, the method 900 may include providing a substrate.The substrate may comport with embodiments described in connection withsubstrate 108 of FIG. 1.

At 904, the method 900 may further include attaching components (e.g.,components 104, 106 of FIG. 1) of a multi-channel modulator driver tothe substrate. For example, the components may be mounted on thesubstrate using a solder surface mount technique or any other suitableprocess. The components may include, first components (e.g., components104) associated with a first channel and second components (e.g.,components 106) associated with a second channel.

At 906, the method 900 may further include attaching an enclosure (e.g.,enclosure 102 of FIG. 1) to the substrate to cover the components of themulti-channel modulator. The enclosure may have at least one wall (e.g.,wall 110 of FIG. 1) that extends from the enclosure to the substrate andmay be disposed between the first components and the second components.In some embodiments, a peripheral region of the enclosure may beattached to the substrate using an electrically insulative adhesive andthe wall may be attached to the substrate using an electricallyconductive adhesive. The wall may be attached to a ground structure(e.g., ground strip 126 of FIG. 1) formed on the substrate. In someembodiments, the enclosure may be prepared for attachment by exposingthe enclosure to heat (e.g., baking in nitrogen environment for about 4hours at 100° C.) to drive out any moisture in the enclosure.

At 908, the method 900 may further include attaching the substrate to aprinted circuit board (e.g., printed circuit board 120 of FIG. 1). Forexample, in some embodiments, the substrate may be mounted on theprinted circuit board using a solder reflow process or any othersuitable process. The substrate may include an epoxy material and theenclosure may be fabricated using an electrically conductive polymerthat may resist softening under temperature conditions associated withthe solder reflow process or other mounting process. In someembodiments, the temperature conditions associated with the solderreflow process may include a peak temperature of about 260° C.

Although certain embodiments have been illustrated and described hereinfor purposes of description, a wide variety of alternate and/orequivalent embodiments or implementations calculated to achieve the samepurposes may be substituted for the embodiments shown and describedwithout departing from the scope of the present disclosure. Thisapplication is intended to cover any adaptations or variations of theembodiments discussed herein. Therefore, it is manifestly intended thatembodiments described herein be limited only by the claims and theequivalents thereof.

What is claimed is:
 1. A method, comprising: providing a substrate;attaching components of a multi-channel modulator driver to thesubstrate, the components including at least first components associatedwith a first channel and second components associated with a secondchannel; and attaching an enclosure to the substrate to cover themulti-channel modulator driver, the enclosure having a wall that isdisposed between the first components and the second components, theenclosure and the wall being composed of an electrically conductivepolymer.
 2. The method of claim 1, wherein: the components are attachedusing a solder surface mount technique; and the components areconfigured to emit radio frequency (RF) energy.
 3. The method of claim1, wherein: the wall includes a film composed of a metal that covers atleast a portion of the wall; the substrate includes a ground structuredisposed between the first components and the second components of themulti-channel modulator driver; and attaching the enclosure to thesubstrate includes attaching a peripheral region of the enclosure to thesubstrate using an adhesive and attaching the wall to the groundstructure using an electrically conductive adhesive to couple the filmto the ground structure.
 4. The method of claim 3, further comprising:mounting the substrate on a printed circuit board using a solder reflowprocess, wherein the substrate comprises an epoxy material and whereinthe electrically conductive polymer has a surface resistivity rangingfrom 10 Ohms to 5000 Ohms and resists softening under temperatureconditions associated with the solder reflow process.